Anodizing racks



l. MYIYNES ETAL ANODIZING RACKS Oct. 22, 1963 2 Sheets-Sheet l Filed Dec. 1, 1961 6 M Y s a w 3 m. m M 8 WEN R 0 3 8 0 6 NI. 9 o 4 6 8 Z. W o 2 7 8 .L T. 2 4 O 4 GE A g a m M z m mS Oct. 22, 1963 Filed Dec. 1, 1961 I. MINES ETAL ANODIZING RACKS Fly. 8

2 Sheets-Sheet 2 IN VEN TORS.

IRVING MINES BY SAMUEL MINES ATTORNEY United States Patent 3,10%,658 ANGDIZING RACKS Irving Mines and Samuel Mines, both of Trenton, NJ, assignors to General Plating Company, Trenton, N.J., a partnershi Filed Dec. 1, 1961, Ser. No. 156,306 2 Claims. (Cl. 2&4-297) This invention relates to work-holders, and it particularly relates to work-holders used in anodizing processes.

Anodizing processes generally consist of the production of a protective oxide film on aluminum or other light metals by passing a high voltage electric current through a bath in which the metal is suspended. The bath usually contains sulfuric, chromic or oxalic acid and the sides of the tank often are in an electric circuit whereby they serve as the cathode while the metal workpiece serves as the anode.

Until recent years, the Work-holders for holding the metal workpieces in the bath were generally made of aluminum or the like similarly to the metals being anodized. However, these alminum work-holders tended to form the same oxides on their surfaces as did the the workpieces. Since alminum oxide is electrically nonconductive, the Work-holders, particularly their points of contact with the workpieces, had to be constantly cleaned to remove the aluminum oxide. This not only was a waste of time and labor but resulted in rapid wear of the holders because each time the oxide coating was removed, the metal itself became thinner until it eventually wore out completely.

In recent years, titanium has, to a large extent, replaced aluminum as the material for making anodizing racks or 'workholders. Titanium is superior to aluminum for the purpose because not only is it highly resistant to acids, alkalies and numerous other chemicals but, even when it is oxidized on its surface to form titanium oxide, there is no substantial diminution of the electrical conductivity of the rack since titanium oxide, unlike aluminum oxide, is not a dielectric. However, an important disadvantage in the use of titanium racks lies in the fact that titanium is not a very good electrical conductor so that there must be a solid contact between the titanium and the aluminum workpiece to pass suificient electrical current for the anodizing process. As soon as contact is broken between the titanium holder and the aluminum workpiece, the current arcs and the circuit tends to break down. Even where the space is slight, aluminum oxide builds up and as it does so, the amperage goes down causing arcing and building up of electrical resistance which results in burning and etching of the aluminum workpiece at the points of contact.

For the above reasons, it is necessary to maintain a firm abutment between the rack and the workpiece at the points of contact. This may be accomplished by bending the titanium rack into a clamping position each time a new workpiece is placed thereon. Unfortunately, however, the passage of electric current through titanium while it is immersed in the anodizing bath tends to take the temper out of it, causing a tendency to straighten it out, and it soon becomes impossible to retain the resiliency or flexibility needed to provide effective spring clamping action. For this reason, titanium anodizing work-holding racks have not, heretofore, been as effectively used as would otherwise have been the case.

It is one object of the present invention to overcome the aforesaid disadvantages by providing a titanium workholding rack which is always under resilient or flexible clamping pressure in the anodizing bath regardless of the length of time to which it has been subjected to the passage of electrical current.

3,198,353 Patented Get. 22, 1963 Another object of the present invention is to provide a titanium work-holding rack of the aforesaid type which is relatively simple in construction, inexpensive to manufacture and easy to use.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following description when read in conjunction with the accompanying drawings wherein:

FIG. 1 is a sectional view of a tank containing an anodizing bath in which is shown a side elevational view of a workholding rack embodying the present invention, said rack supporting a workpiece also shown in side elevation.

FIG. 2 is an enlarged, detailed, side elevational view of the work-holding rack shown in FIG. 1.

FIG. 3 is a fragmentary elevational view taken on line 3-3 of FIG. 2.

FIG. 4 is a sectional view taken of line 4--4 of FIG. 2.

FIG. 5 is a sectional view taken on line 55 of FIG. 2.

FIG. 5A is a view similar to FIG. 5, but showing a variation of the device embodied in FIG. 5.

FIG. 6 is a side elevational view, similar to FIG. 2, but showing a modified form of rack embodying the present inevntion.

FIG. 7 is a sectional view taken on line 7-7 of FIG. 6.

FIG. 8 is a side elevational view, similar to FIGS. 1 and 7, of a third form of rack embodying the present invention.

FIG. 9 is an edge view of the device of FIG. 8.

FIG. 10 is a sectional view taken on line 10-10 of FIG. 9.

FIG. 11 is an enlarged, fragmentary side elevational view of a modified form of the device shown in FIG. 8.

FIG. 1-2 is a view, similar to FIG. 11, of another I modified form of the device shown in FIG. 8.

FIG. 13 is a view, similar to FIG. 11, but showing yet 7 another modified form of the device shown in FIG. 8.

Referring now in greater detail to the various figures of the drawings wherein similar reference characters refer to similar parts, there is shown in FIG. 1 a tank '10 containing an acid bath 12 in which is removably positioned a supporting frame 14 to which are attached work-holding racks generally designated 16.

Each rack 16 comprises a vertical titanium strap 18 having a bent upper portion 20 at the upper end of which is provided an outwardly inclined strip or flange 22 forming an undercut, generally V-shaped groove 24 thereunder adapted to hold an edge portion of a workpiece. The strap 18 is connected to the frame 14 by any desirable means such as rivets or bolts extending through holes 26 in the strap. It may also be attached by welding or the like.

At its lower end, the strap 18 is provided with a lateral flange 28 (as best shown in FIG. 5) and this flange 28 supports a horizontal strip 30, also made of titanium. The strip 30 is bent into a shape constituting a low, straight center portion, which is the portion welded to and supported by the flange 28, and two upwardly-inclined arm portions extending in opposite directions from the center portion. The outer ends of the upwardly-inclined arm portions are somewhat flattened, as at 32, and these portions 32 each support a titanium contact plate 34 having a bottom flange 36 to which the corresponding portion 32 is welded or otherwise secured. Each plate 34 iSwPIOVidfid with a diagonally upwardly extending titanium strip or flange 38 forming an upwardly opening V-shaped groove 4th adapted to releasably retain an edge portion of a workpiece.

Connected to and depending from the strap 18 is a finger 42 having a lateral flange 44 (as best seen in FIG. which releasably supports the central portion of a leaf spring assembly 46. The leaf spring assembly 46 comprises a spring metal strip 47 coated with any desirable electrical insulation 48. The spring 46 is provided at each end with a bend '59 for applying pressure against the corresponding plate 34. This pressure constant between the bends 50 and the plate 34 also serves to clamp the leaf spring assembly in place on the flange 44, the central portion of the leaf spring assembly resting on and being supported by the flange 44 (as best seen in FIG. 5).

In operation, a workpiece of aluminum or the like, indicated at 52 (in FIG. 1), is inserted between the flanges 22 and 38 of one or more racks 16 prior to immersion of the rack-holding frame 14 into the bath 12. When so inserted, the spring 46 automatically exerts a constant pressure on the plates 34 to hold the workpiece 52 tightly clamped within the grooves 24 and 40 of the flanges '22 and 38. There is, therefore, no possibility of spacing between the workpiece and the contact points of the rack. Furthermore, since the spring 46 is electrically insulated, there is no passage of electrical current therethrough and, consequently, no loss of temper, so that the spring retains its flexibility for a substantial period of time.

As illustrated schematically in FIG. 1, the frame 14 is connected through wiring '54 and the tank 16 through wiring 56 to a source of electrical energy (not shown) whereby the frame 14 becomes the anode and the tank It) becomes the cathode portion of the circuit. The connection between the straps 18 of the racks 16 and the vertical posts of the frame 114 are electrically conductive so that the racks also become part of the anode portion of the circuit.

Although it is preferable to insulate the spring 46, as described above, it is also possible to use the spring without insulation. This is indicated in FIG. 5A where the spring 58, similar to spring 46, is shown without insulation. In this uninsulated form, there is some shunting of current through the spring 58 but since the main current flow remains through the strip 30, there is not sufficient current flow in the spring 58 to materially alter its temper except over relatively long periods of time.

In FIGS. 6 and 7 there is shown a modified form of the invention wherein the rack, generally designated 69, comprises a titanium strap 62, similar to strap 18 of the rack 16. The strap 62 is provided with a bent upper portion 64 having a downwardly-inclined titanium flange 66 similar to flange 22. The strap 62 also has holes 68 similar to holes 26.

The lower end of strap 62 is provided with a lateral flange 70, similar to flange 44, and this flange 70 supports an upwardly-bowed support 72 comprising a spring metal strip 74 coated with any desirable electrical insulation 76 (note FIG. 7). The support 72 is connected to the flange 7!} by means of electrically insulated bolts 78 and nuts 80.

The outer ends of the bowed support 72 are connected by electrically insulated bolts 82 and nuts 84 to the lateral flanges 86 of corresponding titanium contact plates 88 similar to plates 34. The plates 88 also have upwardlyinclined titanium flanges 90 defining upwardly-opening V-shaped grooves 92 similar to flanges 38 and grooves 40 in the first-described form of the invention. Since the contact plates 88 are insulated from the support 72, the electrical circuit is established only when the workpiece is in place, the workpiece acting as the electrical connection between the strap 62 and the plates 38.

The device shown in FIG. 6 is utilized in similar manner to that of FIG. 2. However, it is simpler and less expensive in construction because it does not require a separate spring such as the device of PEG. 2, the part 72 4 being itself both a contact holder and a spring. It does not, however, have the advantage of the first-described device wherein the spring can eventually be replaced if damaged or otherwise worn without discarding the entire rack.

In FIGS. 8, 9 and 10 there is shown a further modified form of the invention comprising a rack, generally designated 94, which includes a titanium strap 96 similar to straps 13 and 62 previously described. This strap 96 has an upper bent portion 98 to which is connected a downwardly-inclined flange 10d defining a downwardly opening groove 192. The strap 96 is also provided with holes 104 similar to holes 26 and 68 and utilizable for the same purpose. At its lower end, the strap 96 is provided with a lateral flange 106 on which rests a looped flexible strip of titanium 108. The loop 108 is provided at its upper portion with a pair of bent lugs 110 (best seen in FIG. 10) and these lugs 110 form a collar for slidably securing the loop .108 to the strap 96.

The loop 108 carries a titanium contact plate 112, similar to contact plates 34 and 88 and similarly provided with an upwardly inclined titanium flange 114 defining an upwardly opening groove 116. The loop 108 itself is normally flexed radially outward by leaf spring 118 connectecl to the inner surface of the loop by electrically insulated blocks 120.

The device illustrated in FIG. 11 is identical to that of FIGS. 8-10 except that the loop 122 is flexed outwardly by a block of resilient material 124 made of rubber or the like. This resilient block 124 is substituted for the leaf spring 118 and requires no additional insulation because it is itself electrically non-conductive.

In FIG. 12 there is illustrated a device identical to those of FIGS. 8 and 11 except that the loop 126 is flexed outwardly by one or more coil springs 128 which are held between oppositely disposed electrically insulated followers 130 connected to the inner surface of the loop.

Although the work-holding racks illustrated in FIGS. 8-12 comprise endless loops having separate auxiliary spring means urging them radially outward, and although such construction is preferable for most eflicient utilization of the invention, it is possible to eliminate the auxiliary spring means and utilize the inherent flexibility of the loop for the same purpose. This is possible because the endless configuration of the loop provides an inherent physical counterforce against the tendency of the electrical current to remove the temper and straighten out the titanium strip while it is in the bath. This, of course, tends to set up somewhat more internal stress in the titanium strip than when using the auxiliary spring means, as in the preferable form of the invention, but it is simpler and less expensive than the device using the auxiliary spring. This form of the invention is shown in FIG. 13 where all the parts are identical with the devices of FIGS. 8-12 except that the titanium loop 132 is flexed radially outward by its own inherent flexibility when formed into the looped configuration.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

The invention claimed is:

1. An anodizing work-holding rack comprising an elongated titanium support, a first titanium work-supporting contact on said support, a flexible titanium contact holder on said support, said contact holder being electrically connected to said support and having a second titanium work-supporting contact thereon in spaced relation to said first contact and movable toward and away from said first contact by the flexing of said contact holder, 21 separate spring mounted on said support, said spring having an abutment portion in spring engagement with said contact holder at a position wherein it biases said second contact on said contact holder into a predetermined opposed position relative to said first contact, and said spring being electrically insulated from said support and from said contact holder.

2. An anodizing work-holding rack comprising an elongated titanium support, a titanium work-supporting contact on said support, a flexible titanium strip on said support, said strip being spaced from said contact and extending laterally from at least one side of said support to provide at least one free end portion and being electrically connected to said support, a separate leaf spring mounted on said support, said leaf spring eing spaced from said titanium strip, an abutment portion on at least one end of said leaf spring, said abutment portion being in spring engagement with said free end portion of said titanium strip biasing said free end portion into a predetermined 6 position, and a second titanium work-supporting contact on said free end portion in spaced relation to said abutrnent portion of said leaf spring and in opposed relation to said first-mentioned contact, said leaf spring being electrically insulated from said support and from said strip.

References Qited in the file of this patent UNITED STATES PATENTS 1,503,396 Viog-t July 29, 1924 2,346,386 Nankervis Apr. 11, 1944 2,999,802 Gault' Sept. 12, 1961 3,033,776 Rosner May 8, 1962 3,035,999 Sharon et a l. May 22, 1962 

1. AN ANODIZING WORK-HOLDING RACK COMPRISING AN ELONGATED TITANIUM SUPPORT, A FIRST TITANIUMN WORK-SUPPORTING CONTACT ON SAID SUPPORT, A FLEXIBLE TITANIUM CONTACT HOLDER ON SAID SUPPORT, SAID CONTACT HOLDER BEING ELECTRICALLY CONNECTED TO SAID SUPPORT AND HAVING A SECOND TITANIUM WORK-SUPPORTING CONTACT THEREON IN SPACED RELATION TO SAID FIRST CONTACT THEREON IN SAPCED RELATION TO SAID FIRST CONTACT AND MOVABLE TOWARD AND AWAY FROM SAID FIRST CONTACT BY THE FLEXING OF SAID CONTACT HOLDER, A SEPARATE SPRING MOUNTED ON SAID SUPPORT, SAID SPRING HAVING AN ABUTMENT PORTION IN SPRING ENGAGEMENT WITH SAID CONTACT HOLDER AT A POSITION WHEREIN IT BIASES SAID SECOND CONTACT ON SAID CONTACT HOLDER INTO A PREDETERMINED OPPOSED POSITION RELATIVE TO SAID FIRST CONTACT, AND SAID SPRING BEING ELECTRICALLY INSULATED FROM SAID SUPPORT AND FROM SAID CONTACT HOLDER. 